Common methods of surface passivation techniques include SiO2, SiNx, SiO2/SiNx stack, and a-Si:H formed by: plasma enhanced chemical vapor deposition (PECVD); and hot wire chemical vapor deposition (HWCVD).
U.S. Pat. No. 5,580,828 disclose a method of chemical surface passivation by using a solution of iodine and ethanol, a solution of concentrated alkaline such a ammonia, sodium and potassium-hydroxide for n-type specimens, or, for either type specimens, and a solution of HF at about 40% m/m so as to reduce surface recombination velocities to 10 cm/second or less.
A low temperature composite passivation film is deposited over a semiconductor device at temperatures <150° C. in U.S. Pat. No. 5,903,047 by first forming a hydrogenated amorphous silicon nitride (a-SiNx:H) film over the semiconductor device and then forming a very thin layer (>6.4 nm) of an amorphous silicon hydride (a-Si:H) film over the a-SiNx:H film to prevent oxidation of the semiconductor device due to percolation of moisture, and maintain the electric properties and stability of the semiconductor device.
U.S. Pat. No. 5,507,880 disclose a solar module comprising a glass substrate having thereon:
(a) a conductive metal oxide layer;
(b) an amorphous semiconductor layer;
(c) a back metal electrode; and
(d) a passivating resin layer,
wherein the passivating resin layer comprises a hydrocarbon-based water vapor barrier layer having a permeability to water vapor of not more than 1 g/m2 day measured at a thickness of 100 μm, and wherein the water vapor barrier layer comprises a polymer selected from the group consisting of polyisobutylene, polyisoprene, modified polyisoprene, polybutene, polybutadiene, and modified polybutadiene.
There is a need in the art of preparing crystal silicon surfaces to provide good surface passivation since the direct growth of a-Si:H on c-Si does not generally produce good surface passivation.